EXTERNAL ANATOMY OF INSECTS. 383 



C Metasternum (the Melasternum). The central and 

 often elevated part of the Mesostet/iium. Its anterior 

 niucro, in Coleoptera, often meets the posterior one 

 of the Mesosternwn, and sometimes appears to form 

 one piece with it, as in Hydrophilus, and many 

 Lamellicorn beetles. Sometimes, as in Cetonia vit- 

 ticollis, it even passes between the arms, and covers 

 the Prosternum, or supplies its place. Behind, it 

 often terminates in a bifid mucro. It is not present 

 in many Orders : as in the Hymenoptera, Diptera, 

 &c. a It includes the Pectines. 



a Pectines (the Pectines). Two moveable processes, 

 fixed one on each side by its base below the posterior 

 legs to theMeta sternum in Scorpio: on the lower side 

 is fixed a series of parallel biarticulate processes, re- 

 sembling the teeth of a comb b . 



D Postfurca (the Postfurca). A process of the En- 

 dosternum, terminating in three subhorizontal acute 

 branches, resembling the letter Y, and forming an 

 acute angle with the Endosternum, to which the 

 muscles that move the hind-legs, &c. are affixed c , 



E Opercula (the Opercida). Plates that cover the 

 vocal spiracles in humming insects ; and likewise 

 two large cartilaginous plates fixed to the posterior 

 part of the Postpectus, which cover the Tympana 

 in male Tettigonia F. d Perhaps these may be re- 

 garded as a kind of Metapnystega in a new situ- 

 ation. 



F Pedes Postici (the Hind-legs). The pair of legs 



a Plates VIII. IX. of. b Plate XXVII. Fig. 50, 



c Plate XXII. Fig. 3. b f . 



d Plate VIII. Fig. 18; and XXII. Fig. 13. cf. 



